Dependence of rain attenuation and cross-polarization on drop size distribution

Attenuation and cross-polarization due to precipitation are calculated for five drop size distribution functions, namely the Laws-Parsons, Marshall-Palmer, Joss drizzle, Joss thunderstorm, and a renormalization of the latter. Propagation paths from the Communications Technology Satellite and Comstar D1 synchronous satellites to Ottawa are considered. Clear weather antenna isolation effects are included in the results. It is found that various drop size distributions introduce substantial deviations only in the attenuation versus rain rate curves. A proper normalization of the Joss thunderstorm model is important for attenuation. The deviations are much less in the cross-polarization versus attenuation plots, which are close together for all five drop size distributions. This is so even for the thunderstorm model at 28.56 GHz of Comstar D1, where the differential phase per unit length is decreasing at high rain rates. Unexpectedly, it is also found that for attenuation values not too large, the thunderstorm model provides less depolarization for a given attenuation as compared with the other models.